Sheep estrosis: description and parasitology, symptoms and treatment, prevention

Estroz is an entomotic disease that occurs in sheep as a result of infection with the larvae of the sheep gadfly. Parasites affect the nasopharynx of the animal - they live in the frontal, maxillary sinuses, cavities of the horn processes, the ethmoid bone, in severe cases the brain is involved in the process. Intense inflammation of the epithelium of the upper respiratory tract, if not diagnosed and treated, can cause a decrease in productivity and death of livestock.

Insect description

Nasopharyngeal gadflies belong to the family Oestridae, a subfamily of insects from the Diptera order.In parasitological sources, insects are described as flies about 12 millimeters long, with a yellow head, and large black eyes. The color of the abdomen is blue, the legs are short, orange, the wings are transparent. The body of the gadfly is covered with fine hair, which is why it resembles a bumblebee. Mouth organs are poorly developed.

Gadfly is able to live from three to twenty days, after which its weight is reduced by a third. Under unfavorable climate conditions, the insect freezes, the life cycles inside its body slow down. Nasopharyngeal gadflies are viviparous. The female can spray the larvae right on the fly into the nostrils of livestock in large quantities, from where they penetrate into the nasal and frontal sinuses, into the throat.

Sheep gadflies fly during the hottest time of the day - from 9 am to 5-6 pm. The summer of gadflies begins when the soil warms up to 17 ^{oC and lasts 15-18 days.}

Stages of parasite development

Gadflies are insects characterized by a closed chain of transformations. The complete life cycle is the path from the larva to the adult stage. The three stages of insect formation are distinguished by characteristic shapes:

1. The larvae of the first stage before molting reach 4-5 millimeters in length and 0.34 millimeters in width. They are whitish in color with two dark chitinous hooks at the anterior end and numerous spines scattered throughout the body. With hooks, the larvae firmly attach to the mucous membrane of the turbinates and the ethmoid bone, causing catarrhal, and then serous-purulent rhinitis.
2. At the second stage of development, the larvae molt, turn white, their length is 5-12 millimeters, their width is up to 3 millimeters. In the spring, being in the frontal sinuses and cavities of the horny processes, the larvae molt again and turn into the third stage. The nutrition of the larva is carried out by the tissues and fluids of the host's body. It dissolves solids with special dermatolytic enzymes.
3. At the final stage of development, the parasite larva reaches sizes up to 30 millimeters in length and 3-10 millimeters in width. Two spiracles are located at the posterior end of the body of the larva.When warm stable weather sets in, the gadfly larva migrates in the opposite direction, entering the nasal cavity, from where, when a sheep sneezes, it falls to the ground, burrows into the soil and pupates.

The pupa is painted dark gray, then becomes brown. Its dimensions are 12 mm long, 5 mm wide. At the upper end of the pupa there is a lid through which the adult formed insect (imago) emerges. Development takes from two days to two weeks.

Symptoms of estrosis

Of the total number of larvae that have invaded the respiratory mucosa of sheep, only about 20% reach the next developmental phases. The rest die and come out with nasal mucus during the sneezing and snorting of the animal in the first stage. Introduced parasites are fixed on the mucous epithelium, leading to its injury and intense inflammation, the release of mucopurulent contents from the nasal passages.

The main sign that estrosis infection among sheep will soon begin is a noticeable change in the behavior of livestock. Animals huddle together, look frightened and restless, shake their heads down, step over their limbs. 2-4 days after the female gadfly attacked the sheep, the development cycle of the larvae begins.

The first symptoms of infection appear in cattle on the 5-6th day after infestation. The main signs of estrosis include:

• frequent sneezing and snorting of sheep - this is how they try to free the nasal passages from parasite larvae that got there;
• a sharp increase in the amount of exudate secreted from the nostrils - immediately after infection, it has a mucous, liquid consistency, after which it becomes thick, mixed with pus;
• nose engorgement and swelling near the nostrils - a crust of drying serous-purulent secretions forms along their edges;
• difficulty breathing with constant snoring - observed due to the narrowing of the lumen of the nasal openings, intense inflammation of the mucosa;
• increased submandibular lymph nodes;
• high temperature;
• deterioration of the animal's condition, loss of strength.

In the advanced stage of estrosis, the lining of the brain is affected. Against the background of general intoxication and damage to brain structures, coordination of movements is disturbed, convulsive seizures are possible. Sick sheep lag behind the herd, make arena movements. In a severe form of pathology, the animal has paresis (decrease in muscle strength) and paralysis of the limbs, in the absence of treatment, death occurs after 3-5 days.

Diagnostic Methods

An experienced veterinarian can diagnose estrosis in sheep by a combination of clinical signs. Sometimes a trial irrigation of the nasal passages with insecticidal solutions is required - while the larvae fall into the external environment. You can conduct an intradermal test (allergic research technique). Differential diagnosis is important - sheep estrosis is often confused with coenurosis. But, unlike estrosis, with coenurosis, animals do not have a runny nose and nasal discharge, but only focal thinning of the cranium.

Estrosis can be diagnosed after the death of a sheep - inside the respiratory tract larvae are 12-15 millimeters in size.

Estrosis treatment

There are several effective drugs that have almost 100% effect on gadfly larvae:

• "Cyflunit Flock" - a preparation in the form of a spray with a volume of 500 milliliters, completely ready for use. On the skin along the spinal column, it is enough to apply 7 milliliters of the product to provide 4 weeks of insect protection;
• "Ivermek" is an injectable medication, which includes the component ivermectin and vitamin E. One injection is given with the drug, the second injection is repeated after 8 days. Substances are quickly absorbed, there are no seals and abscesses at the injection site. In addition to gadflies, the product is used to combat nematodes that affect the stomach and intestines, lice, mites;
• "Clozatrem" is an injectable drug based on closantel. Thanks to this component, already 10 hours after the first injection, you can get rid of the invasion of gadfly worms, nematodes, trematodes and other parasites;
• "Butox" - a tool with insect-acaricidal properties. It is a light yellow oily liquid that dissolves in water. Apply the drug in a diluted form, by spraying or bathing.

Timely initiation of estrosis therapy will eliminate larvae in the nasal sinuses of sheep, minimize the clinical manifestations of the disease and prevent mortality.

Prevention of occurrence

As a preventive measure for sheep with estrosis, it is recommended to regularly inspect livestock holding areas for pupae and adult gadfly. Near flocks, it is useful to install shields for planting insects, having previously treated them with whitewash with the addition of insecticides.

Early treatment of livestock with Clozatrem or Ivermek will protect sheep from gadfly attacks. Protective equipment should be applied and pens should be inspected for pupae and adult insects regularly from May to September.

Recommended